Free Lord Foul's Bane by Stephen R. Donaldson

looking for something, but he was too preoccupied to wonder what she was doing. After an intense scrubbing he let his hands rest, and rolled up his sleeves to inspect his elbows. They were red and sore, but the skin was not broken.
When he pulled up his pant legs, he found that his shins and knees were more battered. The discoloration of his bruises was already darkening, and would be practically black before long; but the tough fabric of his trousers had held, and again the skin was unbroken. In their way, bruises were as dangerous to him as cuts, but he could not treat them without medication. He made an effort to stifle his anxiety, and turned his attention back to his hands.
Blood still oozed from the heels and fingertips, and when he washed it off he could see bits of black grit lodged deep in some of the cuts. But before he started washing again, Lena returned. Her cupped hands were full of thick brown mud. “This is hurtloam,” she said reverently, as if she were speaking of something rare and powerful. “You must put it on all your wounds.”
“Mud?” His leper's caution quivered. “I need soap, not more dirt.”
“This is hurtloam,” repeated Lena. “It is for healing.” She stepped closer and thrust the mud toward him. He thought he could see tiny gleams of gold in it.
He stared at it blankly, shocked by the idea of putting mud in his cuts. 
“You must use it,” she insisted. "I know what it is. Do you not understand? This is hurtloam. Listen. My father is Trell, Gravelingas of the rhadhamaerl . His work is with the fire-stones, and he leaves healing to the Healers. But he is a rhadhamaerl . He comprehends the rocks and soils. And he taught me to care for myself when there is need. He taught me the signs and places of hurtloam. This is healing earth. You must use it."
Mud? He glared. In my cuts? Do you want to cripple me?
Before he could stop her, Lena knelt in front of him and dropped a handful of the mud onto his bare knee. With that hand free, she spread the brown loam down his shin. Then she scooped up the remainder and put it on his other knee and shin. As it lay on his legs, its golden gleaming seemed to grow stronger, brighter.
The wet earth was cool and soothing, and it seemed to stroke his legs tenderly, absorbing the pain from his bruises. He watched it closely. The relief that it sent flowing through his bones gave him a pleasure that he had never felt before. Bemused, he opened his hands to Lena, let her spread hurtloam over all his cuts and scrapes.
At once, the relief began to run up into him through his elbows and wrists. And an odd tingling started in his palms, as if the hurtloam were venturing past his cuts into his nerves, trying to reawaken them. A similar tingling danced across the arches of his feet. He stared at the glittering mud with a kind of awe in his eyes.
It dried quickly; its light vanished into the brown. In a few moments Lena rubbed it off his legs. Then he saw that his bruises were almost gone- they were in the last, faded yellow stages of healing. He slapped his hands into the stream, washed away the mud, looked at his fingers. They had become whole again. The heels of his hands were healed as well, and the abrasions on his forearms had disappeared completely. He was so stunned that for a moment he could only gape at his hands and think, Hellfire. Hellfire and bloody damnation. What's happening to me?
After a long silence, he whispered, “That's not possible.”
In response, Lena grinned broadly.
“What's so funny?”
Trying to imitate his tone, she said, “I need soap, not more dirt.” Then she laughed, a teasing sparkle in her eyes.
But Covenant was too full of surprise to be distracted. “I'm serious. How can this happen?”
Lena dropped her eyes and answered quietly, “There is power in the Earth-power and life. You must know this. Atiaran my mother says that such things as hurtloam, such powers and mysteries, are in all the Earth- but we are blind to them